This invention relates to the grounding of electrical connectors, and more particularly to apparatus for cost-effectively creating a high quality ground connection between a BNC connector and the conductive enclosure of an instrument.
If a coaxial cable is connected to an instrument with inadequate grounding and high frequency signals are present within the instrument, the cable may transmit electromagnetic interference (EMI) into the surrounding environment. Since transmitted EMI is regulated by the Federal Communications Commission (FCC) in the United States and even more strictly in the Federal Republic of Germany by the VDE, Verband Deutscher Elektrotechniker (Association of German Electrical Engineers), such transmissions may constitute an unacceptable behavior of the instrument that renders it unmarketable in a number of important countries.
In many instruments, the BNC connectors are mounted on the conductive instrument enclosure or chassis, and the conductors are then separately wired to a printed circuit board (PCB) within the instrument. Although this process produces excellent grounding, it is very labor intensive and therefore undesirable, if it can be avoided.
Mounting BNC connectors directly on the PCBs generally helps to hold down manufacturing costs, but, when this is done, a suitable means of making a high quality electrical connection to the instrument's chassis (or local earth) ground must be found.
One prior method of grounding BNC connectors to instrument enclosures has been to solder a separate beryllium copper metal sleeve with flared out extensions to each BNC connector. Then, when the instrument cover is pressed against the flared out extensions during assembly, they provide a good electrical contact between the instrument case and the BNC connector. These sleeves were slitted to allow them to fit over the locking pins on the barrel of the female BNC connectors, and, with their flared out extensions, somewhat resemble a crown. While this approach provides a good ground connection, it is far too labor intensive for mass production applications in which the desire is to be inexpensive by requiring limited labor.